1. Field of the Invention
The invention relates to a vehicle bumper structure that includes a pipe member extending along the vehicle-width direction.
2. Description of the Related Art
Vehicle bumper structures that include pipe members have been suggested in recent years.
For example, Japanese Patent Application Publication No. 2000-85496 (hereinafter, referred to as “JP-A-2000-85496”) describes a technology relating to a bumper structure designed to absorb a shock due to a so-called pole collision. According to the technology, a concave having a semi-circle cross section is formed along the vehicle-width direction in the outer face of a bumper reinforcement member, and a relatively short pipe member is welded to the bumper reinforcement member at the lateral center of the concave. After a bumper was assembled, the pipe member is half projected from the outer face of the bumper reinforcement member. If such pipe member collides with, for example, a pole, the collision load is transmitted through the pipe member and then dispersed through the surface of the concave formed in the bumper reinforcement member.
Japanese Utility Model Application Laid-Open Publication No. 64-9857 (hereinafter, referred to as “JP-U-64-9857”) describes a technology relating to a bumper structure that includes a bumper-stay, which connects a front bumper cover and a side member to each other. According to the described technology, a bumper-bar, which is formed of a pipe member, is welded to the end portion of the bumper-stay in advance. The bumper-bar is then placed between horizontal ribs formed on the rear face of the front bumper cover. After that, the bumper-bar is fixed at this position with bolts. With this structure, an airflow, which is coming into the vehicle while the vehicle is moving, is introduced to both the upper and lower sides of the bumper-bar. As a result, the airflow cools an engine more efficiently.
Nowadays, there has been growing demand for the development of a bumper structure, which is provided at a lower cost, lighter, and, more easily assembled, while offering a sufficient level of energy absorption performance.
For example, JP-A-2000-85496 describes a technology in which a pipe member is welded to a bumper reinforcement member. However, this increases the vehicle weight, and complicates the assembly process due to the need for a welding process. According to JP-U-64-9857, a pipe member is used instead of a bumper reinforcement member. However, because a bumper-bar is welded to the end portion of a bumper-stay, the similar problems described above are left unsolved.